Today, as we continue our retrospective look at The Simpsons, we present what we think is the best episode from each of the past 20 seasons. For each season we picked just one episode that we think is the best (which was not an easy task for most seasons). Obviously we're not going to be able to include everyone's favorite episode, since we're leaving off 421 other episodes (this Sunday's "Once Upon a Time in Springfield" is touted as the series' 450th episode -- it's #451 if you count the pilot/special, "Simpsons Roasting on an Open Fire"). But if you really feel strongly about a certain episode feel free to let us know in the comments below.

By the time "The Crepes of Wrath" aired, the eleventh episode in the series, The Simpsons was falling into its groove, showing many signs of the classic series it was to become. The episode features a strong central storyline, with Bart being shipped off to France as an exchange student and being forced to work for two unscrupulous winemakers that mix antifreeze in their wine. The episode's second storyline is just as strong, with the Simpson family taking in an Albanian exchange student named Adil, who turns out to be a spy looking to obtain nuclear secrets from Homer. "Crepes of Wrath" is one of the few Simpsons episodes where Bart seems to genuinely learn something -- he speaks perfect French by the end of the episode (of course, he's never spoken in French since, but hey, you don't use it, you lose it).

The second season was a good time for The Simpsons as the rough animation style from season one was fixed, while the programs writing got a firm grasp on the role of the show. Bringing in random storylines intermixed with thoughtful family driven resolutions, the episodes grew to be more than just popular animation, but good television. Even though there were many great episodes before it, "One Fish, Two Fish, Blowfish, Blue Fish" helped show just how dramatic The Simpsons could be. In the episode Homer is told that he has 24 hours to live after getting poisoned by bad Japanese food, and he decides to spend his last hours on earth living out everything that he has ever wanted to do. Although it may not have had the laugh-out-loud laughs that "Bart the Daredevil" had, it told a better story, and showed that despite being a jerk most of the time, Homer really did want to do right in his life.

Homer's drunken nights at Moe's bar were already a staple of The Simpsons, but this episode was one of the first to really give Moe the spotlight. Of course, it also helped show that he wasn't exactly the most trustworthy guy, as he steals Homer's secret recipe and uses it to turn his bar into a huge success, thanks to the "Flaming Moe" drink. This episode has tons of standout moments, from the appearance by Aerosmith (the first time a musical act of that caliber appeared as themselves on the series); a funny payoff for all of Bart's prank calls to Moe's, when a man named Hugh Jass actually does turn out to be a customer; a deftly done Cheers parody at the height of Moe's success; and Homer turning into a Phantom of the Opera type lunatic, as he shows up at Moe's to reveal the truth to everyone, and unaware that Moe was going to sell the recipe and split the profits with him, inadvertently ruins his own chances to make half a million dollars.

Every minute of the Conan O'Brien-scripted "Marge vs. The Monorail" is filled with humor and spot-on parodies. From the episode's beginning with Homer driving and singing "Simpson, Homer Simpson" to the tune of "The Flintstones," to Marge's closing voiceover covering Springfield's other ridiculous endeavors (ending with an escalator that goes nowhere), there isn't a minute wasted. "Marge vs. The Monorail" is one of the tightest and funniest episodes in the history of The Simpsons, let alone in season four, which contained plenty of other great episodes, including "Kamp Krusty," "Mr. Plow," and "I Love Lisa." Phil Hartman gives a truly superb performance as the shifty monorail salesman, Lyle Lanley -- with his highlight being the Music Man song and dance parody, "The Monorail Song" -- and Leonard Nimoy appears as himself (in one of our Top 25 Guest Appearances), boring his fellow monorail passengers with obscure comments and teleporting out at the end of the episode.

One of the best episodes of the series to this point, "Cape Feare" took the idea of parodying a recent hit film and seamlessly interwove it into the show's own history and characters. Sideshow Bob takes over for Robert De Niro, as a convict released from jail with nothing but revenge in mind, as he plots to kill Bart. From Sideshow Bob's attempts to mockingly laugh at a movie theater being outdone by Homer's own genuine, but ludicrously loud laughs (to the movie Ernest Goes Somewhere Cheap) to Homer bursting in on a frightened Bart ("BartDoYouWantSomeBrownie'sBeforeYouGotoBed?!", "BartDoYouWantToSeeMyNewChainsawAndHockeyMask?!") to a truly legendary bit of physical comedy involving Sideshow Bob and several rakes, this is just a great episode start to finish and helped to cement Sideshow Bob as a classic Simpsons character.

In the hilarious sixth season, we were forced to pick "Treehouse of Horror V." Not only was it the funniest Treehouse of Horror to date, but it also beat out side-splitting episodes like "Itchy & Scratchy Land" and "Bart vs. Australia" to be the best episode of the season. You might be asking yourself: "Which Treehouse of Horror episode was that again?" Instantly recognizable, this episode featured the parody of The Shining ("The Shinning"), a parody of the Ray Bradbury short story "A Sound of Thunder" - with Homer going back in time with the toaster, and the "Nightmare Cafeteria," where the children are served as food. Each of these skits were very funny and they all featured Groundskeeper Willie getting killed by an axe - how can you go wrong with that!

Although there was some good competition - notably "22 Short Films About Springfield" and "Homerpalooza" - "A Fish Called Selma" seemed as if it was the obvious pick. Following the misadventures of Troy McClure, we watch him as he falls in love with Selma while balancing his fragile Hollywood career. This storyline is funny enough, but it is the multiple references to Troy being a deviant (he likes fish) and his acting roles that really make this episode hilarious. In the best scene of the episode (and maybe even the whole show) we watch as Troy McClure performs in a musical adaptation of Planet of the Apes ("I hate every ape I see, from chimpan-A to chimpan-Z").